This invention relates generally to a vehicle sensor assembly and, more particularly, to a vehicle sensor assembly including an integral heating unit.
Proximity detection systems are increasingly included on vehicles. These detection systems supplement the vehicle driver""s vision by sensing the presence of objects which are located in the driver""s blind spots or are otherwise difficult for the driver to see. Typical detection systems include a number of sensors which are positioned at various locations on the vehicle. The sensors can be any suitable sensors, such as ultrasonic, infrared or radar transducers. The sensors are in communication with a central controller, such as a microprocessor or engine control unit. The controller regulates the actuation of a user interface which is configured to generate an audio and/or visual warning to the vehicle driver. If one or more of the sensors detects an object within a predetermined proximity of the vehicle, a signal is transmitted to the controller. The controller processes this signal and transmits a control signal to the user interface. A warning is then generated by the user interface to alert the driver of the presence of the object.
A disadvantage of traditional detection systems is that reliability is often compromised during inclement weather. Ice, frost or snow built up on or around the sensors or the sensor housing impairs the ability of the sensors to operate satisfactorily. For instance, where the sensor is an ultrasonic sensor, accumulated snow or ice on the sensor housing blocks the transmission of signals from the sensor. The accumulation also prevents the sensor from receiving ultrasonic waves deflected from an object near the vehicle. Prevented from reliable signal transmission and receipt, the sensor is rendered useless.
Recent attempts were made to prevent cold weather conditions such as ice and snow from impairing the performance of proximity detection systems. One result of these attempts are detection systems which include a heating element positioned in each sensor housing. The heating element is activated by the controller upon receipt of an appropriate trigger signal. For instance, the controller could be triggered to activate the heating coil if a vehicle external temperature sensor detects a temperature below a predetermined threshold. Once activated, the heating element heats the sensor and the surrounding sensor housing, thus melting the ice and snow.
While such detection systems were created for improved performance, they typically suffer from one or more deficiencies. The heating elements in these systems are generally either too large or poorly positioned. The result is often a sensor which either continuously detects itself or which detects nothing. The former condition results where the heating element deflects signals back to the sensor; the later where the signals are blocked by the heating element but not deflected back to the sensor. Attempts were made to minimize or reposition the heating element to correct this problem. However, these attempts yielded heating elements which were too small or too remote from the front of the sensor to effectively remove built up snow and ice and to maintain the sensor housing free from such accumulation.
This invention is directed to a new and useful sensor assembly. The sensor assembly includes a sensor housing configured for attachment to an external surface of a vehicle. A transducer is positioned in the sensor housing and is configured to receive interrogation signals from a controller. The sensor assembly also includes a heating unit. The heating unit includes a solid, single layer shell configured to receive the transducer. A heating coil is embedded in the shell. The heating coil is configured to radiate heat as a result of current applied across the coil. The radiated heat warms the transducer, causing snow and ice to melt and preventing further accumulation thereon.
The heating unit is created by winding a length of wire around a core to form a work piece. The core is positioned in a mold. Heated plastic material is injected into the mold. The temperature of the heated plastic material is sufficient to melt the core. The result is a solid shell including a heating coil embedded therein.
Owing to the structure of this assembly, a heating unit is created which is suitable for use with various sensor assemblies. Since the heating coil is formed around and supported by a core which is sacrificed during construction, the heating coil can be formed from a delicate wire having a relatively small diameter. Additionally, since the heating coil is formed in the interior of the sensor shell, appropriate sizing of this component will prevent the heating coil from interfering with signal transmission or reception. The result is a heating unit with a heating element which is sized to sufficiently heat the surrounding sensor housing while being appropriately sized and positioned to not interfere with sensor function.